i have configured ser-0.8.11-0 ser-mysql-0.8.11-0. i have configured using how to provided in iptel.org website. my Sjphone authenticated perfectly against mysql database. but while calling to other sjphone it is giving some unusual voice. it is giving strange voice. what could be the problem? is there any thing to configure for voice?

While using Sjphone, On screen it show me (gsm). is that reason for unusual voice. if yes, then how do i solve this problem.